PURPOSE: To improve safety by setting an authentification key in a mobile equipment and a home memory station beforehand and providing an equal ciphered algorithm executing function.

CONSTITUTION: A mobile equipment 1 and a home memory station 2 are respectively set an authentification key 3 and respectively equipped with an equal ciphered algorithm executing function 4, and an authentification request number containing a random number generated by a random number generation part 5 is transmitted from the memory station 2 to mobile equipment 1. Based on this received random number and the authentification key 3, the mobile equipment 1 executes cipher algorithm by the function 4 and transmits an authentification response signal containing the executed result to the memory station 2. A comparison part 6 compares this executed result with the certification key 3 of the memory station 2 and the executed result through the executing function 4 and judges either coincidence or non-coincidence. Therefore, since it is not necessary to hold the secret of the ciphered algorithm and further it is not necessary to execute transmission/reception while directly inserting the secret key to the signal, the safety is improved.